Severe Thunderstorm Warning 64, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
1201 PM MDT Mon Jul 3 2023

.DISCUSSION...(This afternoon through Sunday)
Issued at 1145 AM MDT Mon Jul 3 2023

A deep positively tilted upper level trough extends from a low
near the Hudson Bay down through western WY to Idaho. Southwest
divergent flow aloft across the CWA with ample PVA extending
northeast to the upper Great Plains of the Dakotas. As a result,
expect strong to severe thunderstorms Monday afternoon to develop
and pushing east through sunset with some lingering rain showers
overnight into Tuesday morning. Supported by a shortwave, a vort
max extend off the Bighorns into Montana where better shear will
be for extensive severe weather in a more slight to enhanced area
into northeastern portions of the state. Ample low level moisture
from the southeast will increase instability for the eastern
counties of the CWA with CAPE values up to 1500 J/kg possible.
This initial development could see some isolated supercells that
will have larger hail the main threat with a possible isolated
tornado as well. Confidence is low for tornadoes as the better
environment will be in the Devil's Tower area into the Black
Hills. As storms develop westward to the Idaho state line by mid
to late afternoon, more of a wind threat with possible funnels as
a cluster of storms pushes east across the CWA mainly east of the
Divide to include the southern counties along I-80. Inverted-V
skew-Ts will see damaging wind over 60 mph to possibly 70 mph
gusts as the late afternoon and evening progresses. Towards
sunset, these storms will begin to weaken and move east into the
overnight hours with the cold front nearing the Montana state
line.

The aforementioned front will begin to make its way through the
CWA northwest to southeast by early morning and into the afternoon
hours. Behind the cold front will be scattered rain showers and
cooler temperatures for the afternoon and evening. Ahead of the
front will still see average to above average temperatures with
another round of marginally severe weather along the surface
boundary. Medium confidence as it will all depend on speed of the
front, and currently models are not quite consistent with each
other with this. If it clears before afternoon, no severe storms
will occur but if it slows any, southern and southeastern counties
will see this affect. With frontal forcing, expect some larger
hail and damaging winds as the main hazards.

Otherwise, the active weather pattern will continue through the
end of the workweek with daily afternoon and evening rain showers
and thunderstorms through Friday as the upper level trough
continues to sit to the west. It does gradually fill mid to late
weak with increasing convergence aloft as an upper level high to
the south begins to build northward as time progresses. As a
result, this will extend through the CWA by late weekend ejecting
the trough to the northeast bringing warmer temperatures and dryer
conditions for the next week. CPC even shows in the extended
outlook these warmer than average temperatures and dryer than
average conditions moving forward.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1105 AM MDT Mon Jul 3 2023

Showers and thunderstorms expected to develop this afternoon as a
weather system impacts the area. Strong outflows are the main
concerns with any storms today, with gusts above 50 mph possible
from any storm that develops. Rain chances will continue into the
night for many sites, with VCSH/VCTS conditions continuing into
Tuesday. VFR conditions prevail through today, with brief MVFR
possible if a storm impacts a terminal. Models look to bring in
lower ceilings overnight, with potential for MVFR ceilings at KCPR.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued at 1145 AM MDT Mon Jul 3 2023

Showers and thunderstorms expected this work week daily in the
afternoon and evening hours. Monday will see westerly winds
gusting up to 25-35 mph with relative humidity values dropping to
the 20-30 percent range, below 20 percent for southern counties
towards the Colorado state line. Cooler temperatures expected
Tuesday and Wednesday behind a cold front with gusty north to
northwest winds 20-30 mph but lighter for Wednesday. Active
weather through early weekend before warming and drying out late
weekend and into much of next week.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DISCUSSION...Lowe
AVIATION...Wittmann
FIRE WEATHER...Lowe

Hazardous Weather Outlook
National Weather Service Riverton WY
331 AM MDT Mon Jul 3 2023

WYZ001>020-022>030-041300-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Big Horn Basin-Southwest Big Horn Basin-
Southeast Big Horn Basin-Owl Creek and Bridger Mountains-
Bighorn Mountains West-Bighorn Mountains Southeast-
Northeast Johnson County-Southeast Johnson County-
Teton and Gros Ventre Mountains-Jackson Hole-
Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
331 AM MDT Mon Jul 3 2023

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and tonight.

Strong to possibly severe thunderstorms this afternoon and evening
across the northern half of the state. High wind gusts will be the
most widespread threat, with large hail and an isolated tornado
possible in northwestern areas.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday...Strong thunderstorms possible in the south. Much cooler
East of the Divide.

Thursday and Friday...Scattered showers and thunderstorms will
continue in the afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please report significant
weather.

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